Mine firing control system



Aug. 18, 1959 s Sheets-Sheet 1 7 Filed Jan. 6, 1943 A. HOBBS CHARLES 13, 1959 c. A. HQBBS MINE FIRING CONTROL SYSTEM 5 Sheets-Sheet '2 Fi led Jan. 6, 1943 3mm 014M CHARLES A. HOBBS Aug. 18, 1959 "c. A. HOBBS 2,899,896

MINE FIRING CONTROL SYSTEM Filed Jan. 6, 1943 3 Sheets-Sheet 3 P 1 m onion CHARLES A. HOBBS United States Patent Ofiice 2,899,896 Patented Aug. 18, 1959 MINE FIRING CONTROL SYSTEM Charles A. Hobbs, Charlotte, N-C.

Application January 6, 1943, Serial No. 471,452

16 Claims. (Cl. 102-18) (Granted under Title 35, US. Code (1952), see. 266) This invention relates to submarine mine firing mechanisms of the electromagnetic induction type in which the mine is fired electrically in accordance with a predetermined number of pairs of signals corresponding to a predetermined number of changes in the magnetic field adjacent thereto occurring in predetermined time space relation and in which the mine is unresponsive to additional signals for a predetermined period of time after the first signal of each pair is received. More specifically,

the present invention relates to a mine firing control system in which means are provided for detecting the changing magnetic field adjacent the mine and for storing signal indications corresponding respectively to pairs of signals received in predetermined time space relation, and in which means are provided for exploding the mine when a predetermined number of signal indications has been received.

It is the general practice in systems heretofore employed with an influence type mine such, for example, as a mine controlled by electromagnetic induction caused by variations in the magnetic field adjacent thereto, to employ various devices adapted to prevent the premature detonation of the mine by mine sweeping operations. In the case of magnetic induction mines the mine sweeping operations may comprise heavy current impulses applied to an electrical conductor towed through the water by a vessel, hereinafter referred to as a mine sweeper, the V trailing wire, hereinafter referred to as a sweep wire, being electrically insulated from the sea water except at the furthermost end thereof whereby the flow of current through the sweep wire causes an electromagnetic field to be set up about the wire of suflicient intensity to cause the explosion of an electromagnetic induction type of mine within the vicinity of the sweep wire. Thus in the types of submarine mines heretofore devised employing firing mechanisms controlled by changes in the terrestrial magnetic field there is a possibility that the mines may be exploded by a mine sweeper systematically cruising over the minefield and applying current impulses at periodic intervals of time to the sweep wire trailing from the vessel.

In order to set up an effective magnetic field of considerable magnitude about the sweep wire, it has heretofore been found necessary to apply an electrical current to the sweep wire of such strength that the source of electrical energy therefor is only sufiicient to allow the current to be applied to the sweep wire periodically for short periods of time interspersed with relatively long time intervals during which the magnetic field within the vicinity of the sweep wire is unchanged, in contradistinction to the changes of relatively long duration in the magnetic field caused by the movement of a preponderous mass of magnetic material such, for example, as a vessel within the vicinity of the mine.

In the system of the present invention the mine firing mechanism includes certain magnetic field sensing elements adapted to control a plurality of timing devices and time delay mechanisms operatively connected thereto whereby the explosion of the mine is effected when the aforesaid timing mechanisms and time delay devices have performed a plurality of cycles of operations corresponding in number to the instant setting of a selecting device settable at will to different settings, each of the cycles of operations corresponding respectively to changes of predetermined character in the magnetic field such, for example, as the changes in the magnetic field caused by the movement of a steel vessel or any vessel having a preponderous amount of magnetic material therein past the mine disposed adjacent the path of travel of the vessel. By reason of the timing devices, the time delay devices and the circuit arrangement and connections therebetween, the probability of the mine being exploded as the result of electromagnetic changes received from a sweep wire is extremely remote. Furthermore, in the system of the present invention means are, provided to prevent the premature explosion of the mine as the result of shocks or impulses of pressure received through the water such, for example, as shocks received from countermining operations within the vicinity of the mine.

Furthermore, the mine is rendered absolutely safe for transportation, handling and planting and becomes active when a predetermined period of time has elapsed after the mine has been launched within a body of .water by reason of the provision of certain safety control devices adapted to be operated in response to the pressure of the water within which the mine is launched.

The system of the present invention embodies all of the advantages of the prior devices and the additional advantage of a simple and rugged construction which will be economical to manufacture and possesses the desired qualities of reliability and efficiency in use and in operation.

One of the objects of the present invention is to provide a new and improved mine firing device of the above general character having means for detecting a change in the magnetic field adjacent the device when a predetermined period of time has elapsed after a first change in the magnetic field has been detected and detonating the mine when a predetermined number of pairs of changes in the magnetic field have been received.

Another of the objects is the provision of means set+ table at will for selecting the number of pairs of signals corresponding to changes in the magnetic field adjacent the device necessary to fire the mine.

Another object is the provision of new and improved means for controlling the intervals of time during which signals corresponding to successive changes in the magnetic field adjacent the device are received.

Another object is the provision of new and improved means for controlling and storing a plurality of signal indications corresponding to changes in a magnetic field received during predetermined intervals of time and restoring the controlling means to an initial condition when signals corresponding to any of the changing conditions of the field are not received in regular order within a predetermined time interval.

Still another of the objects is the provision of means to changes in the magnetic field.

A further object is the provision of new and improved means for interrupting an electrical connection between the magnetic fieldsensing device and an electro-responsive device operatively connected thereto until a predetermined period of time has elapsed after the electro-responsive device has been operated by a signal received from the field sensing device.

Still further objects, improvements and advantages will be apparent from the following detailed description taken in connection with the accompanying drawings of which:

' settable at will for controlling the sensitivity of the device Fig. l is a view of a submarine mine employing the system of the present invention and the anchoring means therefor;

Fig. 2 is an enlarged sectional view taken substantially centrally through the mine, and,

'Fig. 3 shows in diagrammatic form the entiresystem.

Referring first to Fig. 1 of the drawings there is shown thereon a submarine mine indicated generally by the numeral 11 Comprising a casing 12 having amooring bale 13 pivotally secured thereto asat 14 and provided,

with an eye or shackle 15 to which is attached one end of a mooring cable 16 adapted to be paid out from a reel 17 within an anchor 18, the reel being locked in any well known manner when a predetermined length of cable has been paid out whereby the mine is adapted to be anchored at a predetermined depth of submersion be-- troduced within the chamber 22, a pair of covers 25 being provided to seal the apertures as by the bolts 26 and gasket 27 arranged between each of the covers and the partition 19. t

The casing 12 is provided with a well 28 within which is arranged a detonator 29 adapted to be moved by a hydrostat 31 within an explosive booster charge 32 arranged within the Well. There is also provided within the chamber 22 a tube or duct 33 extending between the tubular member 21 and the well 28 within which is arranged a cable 34 having a pair of electrical conductors adapted to establish an external electrical circuit to the detonator.

Within the tubular member 21 is arranged an induction pickup or search coil 35, hereinafter referred to as SC, comprising a large number of turns of relatively fine wire arranged about a rod or core 36 of magnetic material suitable for the purpose such, for example, as iron or a material composed of 78% percent nickel and 21 /2 percent iron known in the art by the trade name of Permalloy, a pair of conductors being provided to establish an external circuit connection to the search coil.

There is also securedto the upper portion of the partition 19 a firing control mechanism 37, hereinafter referred to as FM, the mechanism comprising, among other elements, certain time delay devices including a pair of switch stepping devices and certain control .relays therefor which coact to cause an electro-responsive selector switch to be stepped ahead such that the switch wiper thereof moves into engagement with the next succeeding contact of the switch bank whenever the presence of a vessel has been detected by the induction pickup coil SC and a sensitive detecting relay operatively connected thereto, the relay being preferably included within the firing mechanism structure. When the selector switch has stepped ahead to a predetermined setting controlled by the setting of a ship selector switch 38, hereinafter referred to as.S, operatively connected thereto as by the cable 39, a firing circuit is closed from the battery 41, hereinafter referred to as BA, to the detonator 29 thereby causing the mine to explode when a predetermined number of ships have moved past the mine. The switch 38 is arranged within a well and secured in any suitable manner to the mine casing 12 as by the bolts42.

The firing mechanism also preferably includes an anticountermine device comprising a pendulum and a slow releasing relay operatively connected thereto adapted to close a pair of contacts in response'to the operation of the pendulum as a countermine shock or pressure impulse 61 in registered engagementwith the plunger.

4 is received through the water and thereby prevent the sensitive relay from being actuated sufiiciently to close the contacts thereof as a result of the shock, as will more clearly appear as the description proceeds. The battery 41 is normally disconnected from the firing mechanism by the contacts of a clock mechanism 43 adapted to be set in operation in response to the pressure of the water within which the mine is planted and complete a circuit from the battery by way of the cable 44 when a predetermined period of time has elapsed after the mine has been planted. The clock is also provided with a second pair of contacts adapted to be closed momentarily prior to the closing of the battery circuit thereby to restore the electro-responsive selecting switch to an initial starting position priortothe operation of the mine firing mechanism in the event that the switch mechanism should have been moved from the initial position thereof for any cause such, for example, as the result of a shock received at the time of planting of the mine.

The upper portion of the casing 12 is provided with an aperture adapted to be closed by the cover 45 secured thereto as bythe bolts 46, a suitable gasket 47 being preferably provided between the cover and the casing to pre vent the entrance of water withinthe chamber 48 or the 'escape of air therefrom when the mine is submerged within the water. The air chamber 48, it will be understood, is of sufficient size to cause the mine to be positively buoyant and assume an upright position within the water with the induction pickup coil 35 thereof vertical at all times by reason of the pivoted bale 13 employed for escapement mechanismcomprising a pivoted wheel 54 having a pair of 'escapement pins55 thereon adapted to be engaged alternately by the teeth of the escapement gear 56 as the cam is moved from the initial position to the final position thereof. There is also provided a plunger 57 having a pin 58 extending outwardly therefrom adapted to be maintained within the path of travel of a stop member 59 arranged on the wheel 54 by the spring The plunger 57 is operatively connected to a hydrostat arranged within the well 62, Figs. 1 and 2, within the casing 12 of the mine and adapted to be moved inwardly by a hydrostat arranged within the well 62 sufliciently for the pin 58 to be disengaged from the stop member '59 as the hydrostat operates thereby setting the clock in operation after the mine has been launched.

The operation ofthe system will best be understood by reference to Fig. 3 of the drawings on which is shown in diagrammatic form the complete system. Let it be assumed, by way of example, that the selector switch S has been set to position 4, the resistance R has been adjusted in accordance with a predetermined sensitivity of the relay D and that the mine has been launched within a body of water and moored beneath the surface of the Water by the bale 13, mooring cable 16 and anchor 13 and let it further be assumed that the detonator 29 has been moved by the pressure-of the water against the hydrostat 31 to an extended position within the booster charge 32 and that the plunger 57 of the starting clockhas been moved by the pressure of the water against the clock bydrostat sufficiently to move the pin 58 thereof out of engagement with the stop member59 and set the starting clock in operation. When. a predetermined period of time such, for example, as ten minutes has elapsed after the starting clock has been set in operation the switch contacts Athereof are movedby the cam 51 to closed position thereby closing. a circuit from the. positive terminal of battery BA, conductor 63, contacts A of the starting clock, conductor-64, the reset magnet R of switch SS3 from whence the circuit is continued by way of conductor 65 to the negative terminal of battery BA thereby causing the reset magnet R to operate and restore the Wiper of switch SS3 to the initial home position thereof in the event that the Wiper may have been previously moved away from the home position for any reason such, for example, as the shock which the mine receives at the time of launching. As the cam 51 continues to rotate the switch contacts A of the starting clock are moved to open position thereby interrupting the aforesaid circuit to the reset magnet R of the switch SS3 and causing the reset magnet to release.

When the starting clock has operated for an additional period of time such, for example, as twenty-five minutes after the clock has been set in operation the clock contacts B are closed by the cam 51 thereby applying battery from positive terminal of battery BA by way of conductor 63 and contacts B of the starting clock to conductor 66 and thus to the movable contact element of the detecting relay D. The mine is now in readiness to receive a signal from the search coil SC corresponding to a .change in the magnetic field adjacent the mine.

As a vessel approaches within the vicinity of the mine the magnetic field adjacent the mine is altered by the presence of the vessel sufficiently to induce an electromotive force within the search coil SC. This electromotive force causes a current to flow over the following circuit: I one end of the search coil SC, conductor 67, winding of the operate magnet of relay D and variable resistance R in parallel, conductor 68, armatures 69 and break contacts of relay RE in parallel, conductor 71 and thence to the opposite end of the winding of the search coil thereby causing the contact element 72 to be moved into ,engagement with contact 73 or 74, as the case may be. When this occurs, a circuit is closed from the positive terminal of battery BA by way of conductor 63, contacts B of the starting clock, conductor 66, contact element 72 of relay D and contact 73 or 74 thereof, conductor 75, winding of relay RE and thence by way of conductor 65 to the negative terminal of battery BA thereby causing relay RE to operate. As armatures 69 of relay RE move away from their break contacts the circuit to the operate winding of relay D is interrupted but contact element 72 thereof does not move away from engagement with its make contact, however, until the reset magnet RES of relay D is energized.

As armature 76 of relay RE engages its make contact a circuit is closed from positive terminal of battery BA by way of conductor 63, contacts B of the startingclock, conductor 66, armature 77 and break contact of relay REI, conductor 78, armature 76 and make contact of relay RE, conductor 79, armature 81 and break contact of relay TD2, conductor 82, winding of the stepping magnet STP of switch SS1, conductor 83, contact 1 and wiper 1 of switch SS2, conductor 65 and thence to the negative terminal of battery BA thereby operating the stepping magnet of switch SS1. Switches SS1 and SS2 are of the type in which the brushes are stepped ahead to the next succeeding contact of the switch banks when their respective stepping magnets are released and the wipers of switch SS1, therefore, do' not step ahead until the operate circuit to the stepping magnet of switch SS1 is interrupted. Asarmature 84 of the stepping magnet of switch SS1 engages its make contact a circuit is closed from the positive terminal of battery BA by way of conductor 66, armature 84 and make contact of the stepping magnet of the switch SS1, conductor 85, winding ofrelay TD1, the circuit continuing by way of conductor 65 to the negative terminal of battery BA thereby causing relay TD1 to operate.

'As armature 86 of relay TD1 moves into engagement with its'make contact a circuit is closed from'positive battery onconductor 66 by way of the make contact the terminals 2 of their respective switch banksv and armature 86 of relay TD1; conductor 87, winding of relay TD2 and thence by way of conductor 65 to the negative terminal of battery BA thereby causing relay TD2 to operate and move the armature 81 thereof out of engagement with its break contact. As armature 81 moves away from its break contact the operate circuit to the stepping magnet STP of switch SSlis interrupted thereby causing the stepping magnet to release and the switch wipers to he stepped ahead into engagement with As armature 84 of the stepping magnet of switch SS1 moves away from its make contact the operate circuit to relay TD1 is interrupted and relay TDl'releases. Relays TD1, TD2, TD3, and TD4 are slow releasing relays by reason of the provision of a copper sleeve or slug arranged about the core of the electromagnet or by providing the relays with dash pots or other similar time delay mechanisms whereby the release of each of the relays TD1 and TD2 occurs after a suitable delay such, for example, as .25 second and the relays TD3 and TD4 release after a delay of .37 second after the operate circuit thereof has been interrupted. The release of relay TD1 at armature 86 thereof interrupts the operate circuit to relay TD2 thereby causing relay TD2 to release in time delayed relation with respect to the interruption of the operate circuit connected thereto. As armature 81 of relay TD2 moves into engagement with its break contact, positive battery on conductor 66 is applied by way of armature-77 and break contact of relay REL conductor 78, armature 76 and make contact of relay RE, conductor 79, armature 81 and break contact of relay TD2, conductor 82 and thence to the winding of the stepping magnet STP of'switch SS1 from whence the circuit is continued by way of conductor 83, contact 2 and wiper 3 of switch SS1 in parallel with contact 1 and wiper 1 of switch SS2, to negative battery on conductor 65 thereby causing the stepping magnet to operate. By providing a time delay mechanism comprising relays TD1 and TD2 in the manner disclosed the operate circuit to the stepping magnet STP is prevented from being closed for a period of substantially one-half second thereby insuring suflicient time for the switch wipers to he stepped ahead to their next succeeding terminals before the operate circuit to the stepping magnet is again closed.

Contacts 2 to 25 of bank 3 of switch SS1 are electrically connected together and to one end of the winding of the stepping magnet STP of switch SS1 whereby negative battery on conductor 65 is applied to one end of the winding of the stepping magnet of switch SS1 whenever the wipers of switch SS1 are in engagement with any of the terminals 2 to 25 of their respective switch banks. The wipers of switches SS1 and SS2 are preferably of the bridging type adapted to engage the next succeeding terminal of their respective switch banks during the stepping operation of the switch before being moved out of engagement with the preceding bank terminals and, therefore, negative battery is continuously applied to the stepping magnet of switch SS1 by way of wiper 3 of switch SS1 as the wiper traverses contacts 2 to 25 of its associated switch bank.

As armature 84 of the stepping magnet STP of switch SS1 moves into engagement with its make contact positive battery is applied by Way of conductor 85 to the winding of relay TD1 thereby causing relay TD1 to operate and at armature 86 and make contact thereof apply positive battery to the winding of relay TD2 and cause relay TD2 to operate. .As armature 81 of relay TD2 moves away from its break contact the operate circuit to the stepping magnet is interrupted thereby causing the stepping magnet to release and advance the wipers of switch SS1 to their terminals 3. .As armature 84 of the stepping magnet moves away from its make contact the operate circuit to relay TD1 is'interrupted thereby causing relays TD1 and TD2 to release. The release of relay TD2 at armature 81 thereof closes the operate circuit to the winding of the stepping'magnet STP of switch SS1 thereby causing the stepping magnet to operate and move armature 84 thereof into engagement with its make contact. The operation of the stepping magnet of switch SS1 at armature 84 thereof causes relay TD1 to operate and close an operate circuit to relay TD2. Relay TD2 operates and at armature 81 thereof interrupts the operate circuit to the stepping magnet STP of switch SS1 thereby causing the stepping magnet to release and the switch wipers to be stepped ahead into engagement with the contacts 4 of their respective switch banks. As wiper 1 of switch SS1 engages contact 4 of the associated switch bank a circuit is closed from positive battery by way of conductor 63, contactsB of the starting clock, conductor 66, winding of reset magnet RES of relay D, conductor 88, contact 4 and wiper 2 of switch SS1, conductor 65 and thence to negative terminalof battery BA thereby causing the reset magnet to operate and restore the contact element 72 of relay D to the initial unoperated position intermediate the. contacts 73 and 74 and disengaged therefrom. Relay RE is prevented from releasing at this time by the engagement of wiper 1 of switch SS1 with its contact 4-.

As the armature of the stepping magnet of switch SS1 moves away from the make contact thereof the operate circuit to relay TD1 is interrupted thereby causing relay T D1 to release and at armature 86 thereof to release relay TD2. As armature 81 of relay TD2 moves into engagement with its break contact the operate circuit to the stepping magnet of switch SS1 is closed thereby causing the stepping magnet to operate and at armature 84 thereof operate relay TD1. The operation of relay TD1 causes relay TD2 to operate and at armature 31 thereof interrupt the circuit to the stepping magnet of the switch SS1. The stepping magnet now releases thereby advancing the switch wipers into engagement with their respective contacts 5. As wiper 1 of switch SS1 moves away from terminal 4 of the associated switch bank the holding circuit for relay RE is interrupted and relay RE releases and at armature 76 thereof removes positive battery from armature 81 of relay TD2 thereby preventing additional operations of the stepping magnet STP of switch SS1 at this time. As wiper 2 of the switch SS1 moves away from terminal 4 of the associated switch bank the operate circuit to the reset magnet of relay D is interrupted and relay D is now in readiness to respond to a signal received from the search coil SC corresponding to a change in the magnetic. field adjacent the mine.

As wiper 2 of the switch SS1 moves intoengagernent with contact 5 of the associated switch bank a circuit is closed from positive terminal of battery'BA byway of conductor 63, contacts B of the starting clock, conductor 66, armature 89 and break contact of relay TD4, conductor 91, Winding of the stepping magnet STP of switch SS2, conductor 92, armature 93 and break contact of relay REl, conductor94, contact 5 and wiper2 of switch SS1, conductor 65 and thence to the negative terminal of battery BA thereby causing the stepping magnet of switch SS2 to operate when a predetermined period of time such, for example, as two seconds has elapsed after the change in the magnetic field was first detected by the search coil SC and relay D. As armature 95 of the stepping magnet of switch SS2 moves into engagement with its make contact a circuit is closed from positive battery on conductor 66 by way of armature 77 and the break contact of relay REl, conductor 78, winding of relay TD3, conductor 96, make contact and armature 95 of the stepping magnet of switch SS2, conductor 94, contact 5 and wiper 2 of switch SS1, conductor 65 and thence to negative terminal of battery BA thereby causing relay TD3 to operate. The operation of relay TD3 at armature 97 thereof closes a circuit from the negative terminal of battery BA byway of conductor 65, wiper 2 and contact 5 of switch SS1, conductor 94, make contact and armature 97 of relay TD3, conductor 98, winding of relay TD4 and thence to positive battery on conductor 66 thereby causing relay TD4 to operate and at armature 89 thereof interrupt the operate circuit to the stepping magnet STP of switch SS2. As the stepping magnetof switch SS2 releases the wipers thereof are advanced into engagement with contacts 2 of their respective switch banks.

As wiper 3 of switch SS2 moves into engagement with its contact 2 a circuit is closed from the negative terminal of battery BA by way of conductor 65 and the strapped terminals 2 to 25 and 1 to 24 of banks 3 and 4 respectively of switch SS2 to conductor 94 in parallel with wiper 2 and contact 5 of switch SS1 whereby negative battery is continuously applied to the make contact of relay TD3 by wipers 3 or 4, as the case may be, of switch SS2 until wiper 4 moves out of engagement with terminal 24 of the associated switch bank regardless of whet-her wiper 2 of switch SS1 remains in engagement with its terminal 5 during the time the switch SS2 has stepped ahead sufficiently for wiper 4 thereof to pass beyond contact 24 of its associated switch bank. In the assumed example, it will be recalled, the changing magnetic field detected by the search coil SC and relay D was caused by an approaching vessel. The release of the reset magnet RES of relay D in response to the movement of wiper 2 of switch SS1 away from terminal 4 of the associated switch bank removes the restraint from the contact element 72 of relay D which moves into engagement with contacts 73 or 74, as the case may be, in response to the changing magnetic field caused by the moving vessel detected at this time by the search coil SC. The switch SS1 is now caused to advance to the home position concurrently with the step-by-step advance of the wipers of switch SS2 through a complete revolution to the initial home position and, whereas these operations occur concurrently it will, of course, be necessary to describe them successively, the continued operation of the switch SS1 from position 5 thereof being first described.

The operation of the detecting relay D at this time closes a circuit from positive terminal of battery BA by way of conductor 63, contacts B of the starting clock, armature 72 and make contact of relay D, conductor 75, winding of relay RE from whence the circuit is continued by way of conductor 65 to the negative'terrninal of battery BA thereby causing relay RE to operate and at the armature 69 thereof interrupt the circuit connection between the operate winding of relay D and the search coil. As armature 76 of relay RE moves into engagement with its make contact a circuit is closed from positive battery on conductor 66, armature 77 and break contact of relay REl, conductor 78, armature 76 and make contact of relay RE, conductor 79, armature 1i and break contact of relay TD2, conductor 82, winding of the stepping magnet of switch SS1, conductor 83, contact 5 and wiper 3 of switch SS1, conductor 65 and thence to negative terminal of battery BA thereby causing the stepping magnet of switch SS1 to operate. As armature 84 of the stepping magnet moves into engagement with its make contact, relay TD1 operates and at armature 86 and make contact thereof causes the operation of relay TD2. As armature 81 of relay TD2 moves away from its break contact the operate circuit to the stepping magnet is interrupted and the stepping magnet releases thereby causing the switch wipers to be moved ahead into engagement with contact 6 of their respective switch banks.

As wiper 1 of switch SS1 engages its contact 6 a circuit is closed from positive battery on conductor 66 by way of wiper 1 and contact 6 of the switch SS1, conductor75, and thence to one end of the winding of relay RE there by maintaining relay RE operated regardless ofthe operated condition of relay D as wiper 1 traverses contacts 6 to 25 of the associated switch bank. As wiper 2 of switch SS1 moves into engagement with contact 6 of the switch bank a circuit is closed from negative battery on conductor 65 by way of wiper 2 and contact 6, conductor 88 extending to one end of the winding of the reset magnet RES of relay D, the other end of the reset magnet winding being connected to positive battery by way the positive terminal of battery BA by way'of conductor 63, contacts B of the clock, conductor 66, wiper 4 and contact 6 of the switch SS1, conductor 99, winding of the stepping magnet STP of the switch SS3 from whence the circuit is continued by way of conductor 101, break contact and armature 102 of relay REl, conductor 65 and thence to the negative terminal of battery BA thereby causing the stepping magnet of switch SS3 to operate. Switch SS3 is of the type adapted to advance the wiper thereof as the stepping magnet is energized and the wiper of switch SS3, therefore, now steps ahead into engagement with contact 1 of the switch bank. The release of the stepping magnet of switch SS1 at armature 84 thereof interrupts the operate circuit to relay TD1 thereby causing relays TD1 and TD2 to be released in succession. As armature 81 of relay TD2 moves into engagement with its :break contact the operate circuit to the stepping magnet of switch SS1 is again closed thereby causing the stepping magnet to operate. The operation of the stepping magnet at armature 84 causes relay TD1 to operate and close an operate circuit to relay TD2 thereby operating relay TD2. The operation of relay TD2 at armature 81 thereof interrupts the operate circuit to the stepping magnet thereby causing the stepping magnet to release and advance the switch wipers to termi nal 7 of their respective banks. As wiper 4 of switch SS1 moves away from its terminal 6 positive battery is removed from one end of the winding of the stepping magnet STP of switch SS3 thereby causing the stepping magnet to release with the switch wiper resting on contact 1 of the switch bank. The switch SS3 has now stored a signal corresponding to the movement of a vessel past the mine. The wipers of switch SS1 are now stepped ahead by the successive operation and release of relays TD1 and TD2 until contact 25 of the switch banks is reached;

The restore magnet RES of relay D is maintained continuously energized during the travel of the switch wipers to their positions 25 by reason of negative battery applied thereto by way of wiper 2 and the strapped terminals 6 to 25 of the associated switch bank. With the wipers resting'on their contacts 25 a circuit is closed from positive battery on conductor 66 by way of armature 77 and break contact of relay RE1, conductor 78, armature 76 and make contact of relayRE; conductor 79, armature 81 and break contact of relay TD2, conductor 82, winding of the stepping magnet of switch SS1 from whence the circuit is continued by way of conductor 83, terminal 25 and wiper 3 of switch SS1, conductor 65 and thence to the negative terminal of battery BA. The operation of the stepping magnet of switch SS1 causes relays TD1 and TD2 to operate in succession. As armature 81 of relay TD2 moves away from its break contact the operate circuit to the stepping magnet of switch SS1 is interrupted thereby causing the stepping magnet to release and tive switch banks.

advance the switch wipers to their normal or home position with the wipers in engagement with contacts 1 of their respective switch banks. As wiper 1 of switch SS1 moves away from its contact 25 positive battery is removed from one end of the winding of relayRE thereby causing relay RE to release and at armature 76 thereof prevent additional stepping of the switch SS1 at this time. As wiper 2 of switch'SSl moves away from contact 25 of the switch bank negative battery is removed from one end of the winding of the reset magnet RES of relay'D thereby releasing the reset magnet and removing the restraint from the contact element 72. Relay D is now in readiness to receive signals from the search coil SC corresponding to a change in the magnetic field adjacent the mine. As wiper 3 of switch SS1 moves away from its contact 25 negative battery is removed from the stepping magnet of the switch SS1.

Whereas in the foregoing description the operations of the switch SS2 necessary to move the wipers thereof to their terminals 2 have been described in detail, it will,

of course, be understood that switch SS2 is stepped ahead concurrently with the switch SS1 by the successive operations of relays TD3 and TD4 until the wipers 2 and 4 thereof are moved into engagement with terminals 24 of their respective switch banks. Switch SS2, it will be noted, is provided with four wipers of which the wipers 1 and 3 are adapted to engage the contacts of their respective switchbanks during the first half revolution of the wipers and the wipers 2 and 4 are adapted to engage the contacts of their respective switch banks during the latter half of the revolution of the wipers. The switch is, therefore, adapted to step the wipers ahead for fifty successive steps before the wipers are brought to rest in the initial home position thereof with wipers 1 and 3 in engagement with contacts 1 of their respective switch banks and wipers 2 and 4 disengaged from contacts 25 of their respective switch banks. Furthermore, Wipers 1 and 2, it will be noted, are electrically connected together, to contacts 2 to'25 of bank 3 and to contacts 1 to 24 of bank 4 of switch SS2 by the conductor 65 in electrical connection with the negative terminal of battery BA. Wipers 3 and 4 of the switch SS2 are electrically connected together by conductor 94 extending to contact 5 of bank 2 of switch SS1, to the make contact of armature 97 of relay TD3 and to the break contact of armature 93 of relay REl, thereby providing an arrangement in which negative battery is applied continuously to conductor 94 in all positions of the switch SS2 except position 25 and the initial home position.

As the wiper 2 of switch SS2 moves into engagement with its contact 25, a circuit is closed from negative bat tery on conductor 65, wiper 2 and contact 25 of switch SS2, conductor 103, winding of relay REI from whence armature 102 of relay REI moves away from its break contact negative battery is removed from conductor 101 extending to the winding of the stepping magnet STP of switch SS3 but without eflfect at this time as the wipers of switch SS1 are resting on contacts 1 of their respecof relay RE1 with its make contact causes negative battery to be applied by way of conductor 88 to one end of the winding of the reset magnet RES of relay D thereby preventing the operation of relay D sufficiently for the contact element 72 thereof to engage either of its make contacts during the time that relay REl is operated. As armature 93 of relay REl moves away from its break contact into engagement with its make contact the operate circuit to the, stepping magnet STP of switch SS2 is transferred to conductor 104, break contact and armature of the stepping magnet of switch SS2, conductor 94, wiper 4 and contact 25 of switch SS2, conductor 105, contact 1 and wiper 3 of switch SS1 to negative battery on conductor 65 thereby causing the steppingmagnet STP of switch SS2 to operate. As armature 95 of the stepping magnet of switch SS2 moves away from its break contact the operate circuit forthe stepping'magnet is interrupted and the stepping magnet releases thereby advancing the switch wipers 2 and 4 out The engagement of armature 102 ing to one end of the winding of relay REl thereby causing relay RBI to release.

As armature 102 of relay RE]. moves away from its make contact negative battery is removed from conductor 88 thereby causing the reset magnet RES of relay D to release andrelay D to be again in condition to receive a signal fromthe search coil SC. As armature 1920f relay REI engages its break contact negative .batteryis "applied to conductor 101 extending to the stepping magnet STP of switch SS3. The release of relay REl at armature 93 thereof transfers the control of the stepping magnet STP of switch SS2 from the break contact of armature 95 thereof'to contact of bank 2 of switch SS1. battery is again applied to armature 76 of relay RE. A complete cycle of operations of the system in detecting As armature 77 of relay REI releases positive and storing a signal indication of the passage'of a ship past the mine has now beencompleted, the'wipers of switch SS2 are returned to their normal or home posi tion and the wiper of switch SS3 has been moved ahead into engagement with contact 1 of its switch bank. The wipers of switch SS1 are also in their normal or home positions and the switches are brought to rest pending a change in the magnetic field sufficient to cause relay D to operate. The relays TD3 and TD l, as heretofore stated, are slow releasing. relays by reason of the provision of a slug or sleeve of copper about the core of the electromagnet or by the provision of suitable delay I devices such, for example, as dash pots or the like whereby the release of each of the relays occurssubstantially .37 second after the operate circuit thereto has been interrupted, the time of release of relays TD3 and TD4 in succession being approximately .74 second and thus an interval of substantially 35 seconds is required for the switch SS2 to perform a complete cycle of operations.

Let it now be assumed, by way of example, that a second vessel approaches sufiiciently near the mine to cause the detecting relay D to be operated by a change in the. magnetic field sensed by the induction pickup coil SC. When this occurs, the foregoing cycle of operations are repeated, the switch SS1 stepping ahead to position 5 thereby setting the switch SS2 into operation to measure the time interval of substantially 35 seconds during which the detecting relay D is adapted to be operated by a change in the magnetic field caused by the moving vessel. .As relay D operates in response to a signal received from the search .coil SC the wipers of switch SS1 are advanced from their contacts 5 to the initial home position and the wiper of the ship selector switch SS3 is stepped ahead into engagement with contact 2 of the switch bank as Wiper 4 of switch SS1 traverses contact 6 of its switch bank.

With the wipers of switch SS1 in their normal home position in engagement with contacts 1 of their switch banks the wipers of switch SS2'are advanced. one step from position 49 to their initial homeposition, the stepping rate of switch SS1 being controlled by relays TD1 V and TD2 and the stepping rate of switch SS2 from the home position thereof to position 49 by relays TD3 and TDd. Relay REL as in the previous cycle of operations, is operated at the completion of the 49th step of switch SS2. during the time wiper 2 thereof is in engagement with contact "of the associated switch bank. 7

Let it now be assumed that the magnetic field adjacent the mine is changed by the influence of an-electromagnet field set up by the sweep wire of a mine sweeper within the vic nity of the mine sufliciently to cause relay D to operate. As the contactelement 72 of relay D moves to circuit closing position positive battery is applied to relay RE by way of conductors 66 and 75 thereby causing relay RE to operate and at armatures 69 thereof interrupt the operate circuit of relay D. Contact ele' ment 72 of relay D, however, asheretofore stated, does not move awayfrom its make contact until the restore magnet RES .is operated. As armature 76 of relay RE engages its make contact the stepping magnet STP of switch SS1 operates thereby moving armature 84 thereof into engagement with its make contact. Relays TD1 and TD2 operate in succession, relay TD2 interrupting the operate circuit to the stepping magnet of switch SS1 at armature 81 thereof. The stepping magnet is thus stepped ahead to position 2. As armature 84 of the stepping magnet of switch SS1 moves away from itsmake contact the operate circuit to relay TD1 is interrupted thereby causing relays TD1 and TD2 to release.

The foregoing cycle of operationsof relays TD1 and TD2 is repeated until the wipers of switch SS1 engage their contacts 4. When this occurs, positive battery is applied by way of wiper 1 and contact 4 of switch SS1 and conductor 75 toone end of the'winding of relay RE thereby maintaining relay RE operated regardless of the operated condition of relay D. As wiper 2 of switch SS1 moves into engagement with contact 4 of the associated switch bank negative battery is applied by way of conductor 88 to the reset magnet of relay D thereby resetting the contact element 72 thereof. to an initial unoperated position intermediate the contacts 73 and 74 and disengaged therefrom. As switch SS1 steps ahead to position 5 during the next succeeding cycle of operations of relays TD1 and TD2 positive battery is removed from one end of the winding of relay RE therebycausing relay RE to release. and at armatures 69 thereof reestablish an operate circuit from the search coil SC to relay D. As Wiper 2 of switch SS1 moves away from contact 4 of the associated switch bank negative battery is removed from conductor 88 thereby releasing the reset magnet of relay D. Relay D is now in readiness torespond to a signal received from the search coil SC in the event that the magnetic field is changed at this time suificiently to cause a signal to be generated by the search coil when a period of time of substantially two seconds has elapsed after a signal corresponding to the first change in the magnetic field set up by the sweep wire has been received by the search coil and relay D.

As heretofore stated, the electromagnetic signals set 'up by a sweep wire are of relatively short duration and each signalis followed by a relatively long interval of time during which the magnetic field is substantially unchanged. It may, therefore, be assumed that the search coil SC does not generate a current as the result of a changingmagnetic field adjacent thereto of sufficient strength to cause relay D to operate as the wipers of switch SS1 move into engagement with their contacts 5.

As wiper 2 of switch SS1 moves into engagement with contact 5 of the associated switch bank, a circuit is closed from the negative terminal of battery BA by way of conductor 65, wiper '2 and contact 5 of switch SS1, conductor 94, break contact and armature 93 of relay REl, conductor 92, winding of the stepping magnet of switch SS2, conductor 91, break contact and armature 89 of relay TD4, conductor 66, contact. B of the. starting clock, conductor63 and thenceto positive terminal of battery BA thereby causing the stepping magnet ofswitch SS2 to" operate. As armature 95 of the stepping magnet of'switch SS2 moves into engagement with its make contact the operate circuit to relay TD3 is closed thereby causing relay TD3 to operate and at armature 97 thereof operate relay -TD4. As armature 89 of relay TD4 moves away from its break contact positivebattery is removed from one end of the winding of the stepping magnet of switch SS2 thereby causing the stepping magnet to release and advance the switch wipers into engagement with their contacts 2. As armature 95 of the stepping magnet of switch SS2 moves away from its make contact the operate circuit to relay TD3 is interrupted thereby causing relays TD3 and TD4 to release in time delay relation with respect to the interruption of the operate circuit of relay TD3. As armature 89 of relay TD4 moves into engagement with its break contact the operate circuit of the stepping magnet STP of switch SS2 is again closed and the stepping magnet operates. The foregoing cycle of operations of relays TD3 and TD4 is repeated until wipers 2 and 4 of switch SS2 engage contacts 25 of their respective switch banks. When this occurs, negative battery on conductor 65 is applied by way of Wiper 2 and contact 25 of switch SS2, conductor 103 to the winding of relay RE1, the circuit being continued by way of conductor 66 to positive battery thereby causing relay RBI to operate. The operation of relay REl at armatu-re 106 thereof closes a circuit from positive battery on conductor 66, armature 84 and break contact of the stepping magnet of switch SS1, conductor 107, wiper 5 and contact 5 of switch SS1, conductor 108, armature 106 and make contact of relay RE1, conductor 82, winding of the stepping magnet of switch SS1, conductor 83, contact 5 and wiper 3 of switch SS1 and thence to negative battery on conductor 65 thereby causing the stepping magnet STP of switch SS1 to operate. As armature 84 of the stepping magnet moves away from its break contact positive battery is removed at one end of the winding of the stepping magnet of switch SS1 thereby causing the stepping magnet to release and advance the switch wipers to their contacts 6. The release of the stepping magnet at its armature 84 again closes the operate circuit to the stepping magnet and the stepping magnet is thus operated repeatedly by self-interruptions until the switch wipers are advanced to their initialhome positions in engagement with contact 1 of their respective switch banks, the operate circuit to the stepping magnet being interrupted as wipers .3 and 5 of switch SS1 move away from their contacts 25. Switch SS3 is prevented from being stepped ahead as wiper 4 of switch SS1 traverses contact 6 of the associated. switch bank by reason of the operate circuit thereto being interrupted at the break contact of relay REI'.

As wiper 3 of switch SS1 moves into engagement with contact 1 of the associated switch bank a circuit is closed from negative battery on conductor 65 by way of wiper 3.and contact 1 of switch SS1, conductor 105, contact 25 .and wiper 4 of switch SS2, conductor 94, armature 95 and break contact of the stepping magnet STP of switch SS2, conductor 104, make contact and armature 93 of relay REl, conductor 92, winding of the stepping magnet of switch SS2, conductor 91, break contact and armature 89 of relay TD4 and thence to positive battery on conductor 66 thereby causing the stepping magnet of switch SS2 to operate. As armature 95 of the stepping magnet moves away from its break contact the operate circuit of the stepping magnet is interrupted and the stepping magnet releases thereby moving the switch wipers 2 and 4 out of engagement with their contacts 25 and the wipers 1 and 3 into engagement with their contacts 1. As wiper 2 of switch SS2 moves away from its contact 25, relay REl releases. As wiper 4 of switch SS2 moves awayfroin its contact 25 negative battery is removed from armature 95 of the stepping magnet of switch SS2 and the switch wipers thereof are thus brought to rest in their initial home positions.

As relay D operates in response to a change in the magnetic field caused by the movement of a third vessel within thevicinity of the mine, switch SS1 is stepped ahead to position 5 thereby setting switch SS2 in operation, relay D being reset as the wipers of switch SS1 traverse their contacts 4. As relay D operates in response to the changing field detected by the search coil SC during the period of time the wipers of switch SS2 are being advanced to their positions 49, the operation of relay RE causes the wipers of switch SS1 to he stepped ahead under control of relays TDI and TD2 into engagement with their contacts 6 thereby operating the stepping magnet of switch SS3 and advancing the switch wiper into engagement with contact 3 of the associated bank. As wiper 4 of switch SS1 moves away from its contact 6 the circuit to the stepping magnet of switch SS3 is interrupted and the stepping magnet releases. The switch SSl is stepped ahead under control of relays TDI. and TD2 until the wipers of the switch have been restored to their initial position in engagement with contacts 1 of the respective switch banks or until wiper 4 of switch SS2 has been stepped ahead into engagement with its contact 25, whichever is the earlier. As wiper 2 of switch SS2 engages its contact 25, relay REl operates.

In the event that wiper 4 of switch SS2 moves into engagement with its contact 25 before the wipers of switch 1 have reached their home position, a circuit is closed from positive battery on conductor 66 by way of armature 84 and break contact of the stepping magnet of relay SS1, conductor 107, wiper 5 and strapped contacts of 'the associated switch bank, conductor 108, armature 106 and make contact of relay REl, conductor 82, winding of the stepping magnet of switch SS1, conductor 83, the strapped bank terminals and wiper 3 of switch SS1 and thence to negative battery on conductor 65 thereby causing the stepping magnet of relay SS1 to be operated by self-interruptions until the switch wipers are restored to their initial home positions. The operation of relay RBI in response to the movement of wiper 2 of switch SS2 into engagement with its contact 25 causes positive battery to be removed from armature 81 of relay TD2 as armature 77 of relay RE1 moves away from its break contact thereby removing the control of the stepping magnet of switch SS1 from the relays TD1 and TDZ. As the wipers of switch SS1 move into their home position switch SS2 is stepped ahead from position 49 to position 50 with the wipers l and 3 thereof in engagement with their contacts 1 and wipers 2 and 4 disengaged from their contacts 25. As wiper '2 of switch SS2 moves away from itscontact 25 negative battery is removed from the winding of relay REl thereby causing relay RBI to release. As wiper 4 of switch SS2 moves away from its contact 25 negative battery is removed from armature of the stepping magnet of switch SS2 thereby preventing additional stepping of the switch SS2 beyond the home position at this time.

As relay D operates in response to a change in the magnetic field caused by the approach of the vessel within the vicinity of the mine, relay RE operates and causes the wipers to switch SS1 to be stepped ahead under control of relays TDI and TDZ tuttil the switch wipers engage their contacts 5. As wiper 2 of switch SS1 moves into engagement with its contact 4 the reset magnet RES of relay D is operated thereby causing the contact element 72 to be restored to the initial unoperated position intermediate the contacts 73 and 74, relay RE remaining operated by positive battery applied byway of wiper 1 and contact 4 of switch SS1. As wiper 1 of switch SS1 moves away from contact 4 of the associated switch bank the reset magnet of relay D is released and the relay is again in a condition to respond to a signal received from the search coil SC as the result of a change in the magnetic field adjacent the mine caused by the moving is removed from one end of the winding of relay RE thereby causing relay RE to release. As wiper 2 of switch SS1 engages contact of the associated switch bank negative battery is applied to conductor 94 thereby setting switch SS2 into operation substantially two seconds after relay D operated in response to the first signal received from the approaching vessel.

The operation of relay D in response to the changing magnetic field caused by the approaching vessel causes relay RE to operate and at armature 76 thereof apply positive battery on conductor 66 by way of armature 77 and break contact of relay REl, conductor 78, armature 76 and make contact of relay RE, conductor 79, armature 81 and break contact of relay TD2, conductor 82, winding of the stepping magnet of switch SS1, conductor 83, contact 5 and wiper 3 of switch SS1 and thence to negative battery on conductor 65 thereby causing the stepping magnetto operate and at armature 84 and make contact thereof apply positive battery to the winding of relay TDl thus causing relay TD to operate. The operation of relay TDl causes relay TD2 to operate and at armature 31 thereof interrupt the operate circuit to the .stepping magnet of switch SS1 thereby causing the stepping magnet to release and advance the switch wipers to position 6.

Aswiper 4 of switch SS1 moves into engagement with contact 6 of the associated bank a circuit is closed from positive battery on conductor 66 to the winding of the stepping magnet of switch SS3 thereby causing the wiper of switch SS3 to be stepped ahead into engagement with its contact 4. When this occurs, a circuit is closed from positive terminal of battery BA by way of conductor 63, contacts B of the starting clock, conductor 66 to the detonator 29 from whence the circuit is continued by way of conductor 109, wiper of the selector switch S and contact 4, conductor 111, contact 4- of switch SS3 and wiper thereof, conductor 65 and thence to the negative terminal of battery BA thereby causing the detonator 29 to operate and explode the mine beneath a vulnerable portion of the vessel in time delayed relation with respect to the first operation of relay D in response to the changing magnetic field caused by the moving vessel.

Whereas in the foregoing example the fourth ship passing the mine was selected for destruction by the switch S, it will, of course, be understood that this is by way of example only as the number of ships required to pass the mine before the mine is fired may be varied at Will in accordance with the setting of the switch S before the mine is launched. While in the specific arrangement of Fig. 3 a selecting switch S settable to ten different settings is disclosed and the contacts 9 and it) of switch SS3 are connected to the wiper and contact 9 of the switch S and, furthermore, the selecting switch SS3 is settable to ten different settings, it will be understood that this is by way of example only as, if desired, the switches SS3 and S may have a greater or lesser number of selecting positions'without departing from. the principles and the invention herein set forth. Also, whereas relay REl is adapted to operate when wiper 2 of switch SS2 moves into engagement with contact 25 of the associated switch bank, it will be understood that, if desired, the interval of time during which relay D is effective to control the operation of the system after the wipers of switch SSE have moved into engagement with their contacts 5 may be varied at will by merely connecting the appropriate terminal of the switch banks 1 and 2 of switch SS2 to conductor W3 and to the succeeding terminals of the switch bank in such a manner that negative battery is not removed from conductor Hi3 subsequent to the engagement of the selected terminal by the switch wiper 1 or 2, as the case may be, of switch SS2 until wiper 2 moves away from contact 25 of the associated switch bank.

The operation of the system in response to a shoe or impulse of pressure received through the Water as the result of a countermining operation will now be described. The mine firing control mechanism, as heretofore stated, is provided with an anti-countermine device of any suitable type adapted to close a pair of contacts when an impulse or wave of pressure is received through the water and maintain these contacts closed for a period of time suflicient for the pressure impulse to subside sufficiently to prevent movement of the contact element 72 of relay D from the initial unoperated position thereof. Various devices suitable for the purpose are well known in the art to which the present invention pertains, these devices comprising inertia controlled mech anisms, flexible diaphragms, dash pots, escapement mechanisms and the like but I prefer to employ, for the purpose of disclosure, a simple mechanism comprising a slow releasing relay AC controlled by the pendulum P.

The operation of the pendulum in response to the movement of the mine as the result of a countermining operation closes a circuit from positive battery at battery BA by way of conductor 63, contact B of the clock, conductor 66, contacts of the pendulum P, conductor 112, winding of the anti-countermine relay AC, conductor 65 V and thence to the negative terminal of battery BA thereby causing relay AC to operate. Relay AC is of the slow release type by reason of the provision of a slug or sleeve of copper arranged about the core of the electromagnet or a suitable time delay device operatively connected thereto whereby the armature 113 thereof is maintained in continuous engagement with its make contact during the oscillatory movement of the pendulum P sufiicient to engage the pendulum contacts at intervals and for a predetermined period of time thereafter. As armature 113 of relay AC moves into engagement with its make contact a circuit is closed from positive battery on conductor 66 by way of the reset magnet RES of relay D, conductor 88, armature 113 and make contact of relay AC and thence by way of conductor 65 to negative battery thereby causing the reset magnet to operate and prevent movement of the contact element 72 from the initial unoperated position thereof until relay AC releases. An arrangement is thus provided in which relay D is prevented from operating in response to a shock or impact of the pressure wave against the mine or as the result of an electrical signal received through the operate Winding of the relay caused by angular movement of the search coil SC within the terrestrial magnetic field as the result of a countermining operation.

'Briefly stated in summary, the present invention contemplates the provision of a new and improved mine firing system adapted to be controlled by a plurality of changes in the magnetic field received within predetermined intervals of time in which a predetermined number of such changes are required to fire the mine beneath a vulnerable portion of a selected vessel, and in which means are provided for preventing the premature detonation of the mine by mine sweeping operations or as the result of a countermining operation.

While the invention has been described with respect to a particular example thereof which gives satisfactory results, it will be understood by those skilled in the art to which the invention pertains, after understanding the invention, that various changes and modifications may be employed without departing from the spirit and scope of the invention and it is my intention, therefore, in the appended claims to cover all such changes and modifications.

The invention herein described and claimed may be manufactured and used by and for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.

What is claimed as. new and desired to be secured by Letters Patent of the United States is:

1. A submarine mine of the character disclosed arranged Within a magnetic field, means including a sensitive relay adapted to detect a changing conditionwithin said field, a control relay adapted to be operated by said sensitive relay, an electro-responsive selector switch, means including a pair of slow' releasing relays for causing the electro-responsive selector switch to he stepped ahead to a predetermined'setting in response to the operation of said control relay, means controlled by the electroresponsive selector switch for releasing said sensitive relay, a second selector switch, means including a second pair-of slow releasing relays for causing said second selector switch to be stepped'ahead a sufiicient number of steps'to effect a cycle of operations thereof in response to the movement of thelfirst named selector switch to the next succeeding position beyond said predeterminedsetting, means for stepping the firstnamed selector switch beyond said next succeeding position as the sensitive relay operates in responseto a changingcondition within the magnetic field during a cycleof operations of said second selector switch, a third selector switch adapted to be operated bythe first named selector switch as the first named selector switch moves beyond said next succeeding position, a firing circuit having a detonating device therein, a source of electrical power, and means for causing the detonating device to be operated by said source of power when the third selector switch has made a predetermined number of operations.

2. In a submarine mine of the character disclosed arranged within a magnetic field, a pickup coil adapted to generate an electrical signal as the first is changed, a sensitive relay operatively connected to said pickup coil and adapted to be operated thereby, a selector switch having a plurality of wipers'adapted to be stepped ahead into engagement with the contacts of their associated switch banks in succession as the switch operates, means including a slow releasing relay for causing the selector switch to be stepped ahead at predetermined intervals of time in response to the operation of said sensitive relay, a second selector switch having a plurality of switching elements adapted to be stepped ahead when the wipers of the first named switch have engaged a predetermined contact of their respective switch banks, means controlled by the first named switch for restoring the sensitive relay to an initial unoperated position when'the switch has made a predetermined number of operations, means for arresting the step-by-step movement of the wipers of the first named switch in a predetermined position as the second switch is set into operation, means including a slow releasing relay for operating said second selector switch at predetermined intervals of time until a cycle of operations thereof has been completed, a switching device adapted to be advanced in steps corresponding respectively to changes in the magnetic field caused by a plurality of vessels moving injsuccession within the vicinity of the mine, means for causing the wipers of the first named switch to be stepped ahead beyond said predetermined position in response to the operation of said sensitive relay while the second selector switch is performing said cycle of operations, means for causingsaid switching deviceto be advanced one step as the wipers of the first named'lswitch are moved beyond said predetermined posiing means inelfective to detect a change in said magnetic field while the control relay is operated, means controlled by said switchsteppingmechanism for releasing the sen sitive relay when a predetermined period of time has elapsed after a'change in the magnetic field has been sensed, means controlled by said switch mechanism for maintaining the control relay operated untilthe sensitive relay has released and for releasing the control relay in time delayed relation with respect to the release" of the sensitive relay thereby to render the sensing means effective, a second switch steppingmechanism, means including a slow releasing relay controlled by said firstnamed switch mechanism for causing said second switch stepping mechanism to operate successively at' regular predetermined intervals of time untilthe second stepping switch mechanism has completed a cycle of operations, and a third stepping mechanism adapted to he -stepped ahead in response to a changein themagnetic field caused bythe continued movement of the vessel and detected by the sensing means when the sensing means has been rendered eifective during said cycleof operations. i

4. In a submarine mine of the character disclosed, means including an electrical relay for detecting a change in the magnetic field caused by the movement of a vessel within the vicinity ofthemine, a selector switch adapted to be stepped ahead successively to different settings in response to the operation of said electrical relay, means for arresting said selector switch in a predetermined set- H ting thereof, vasecond selector switch adapted to be stepped ahead during predetermined intervals of time as the first switch. moves into said predetermined setting, means controlled by said electrical relay for causing the first named selector switch to be moved beyond said predetermined setting in responseto a change in the magnetic field caused by the continued movement of said vessel during the operation of said second selector switch, electro-responsive means for counting each movement of said first named selector switch from said predetermined setting during the operation of said second switch, and means for exploding the mine when a-predetermined number of said movements have been counted by said counting means. i

5. In a submarine mine of the character disclosed, means including an electrical relay for detecting the movement of a vessel within the vicinityof the mine, means for adjusting the sensitivity of response. of said relay to a predetermined change in the magnetic field adjacent the mine, a control relay adapted to be operated by said electrical relay, said control relay having means for operatively disconnecting the electrical relay from said detecting meansas the control relay operates,-a rotary switch settable to different settings in succession, means including apair of time delay devices controlled by said control relay for operating said rotary switch,

means controlled bythe rotary switch for releasing-said sensitive relay and said control relay when the rotary switch has, been stepped ahead -to apredeterminedsetting, a second rotary switch adapted to beset in operation by the first named rotary switch in predetermined time delay relation with respect to the-operation of said control relay, means for operating said second rotary switch at regular predetermined intervals of time thereby to measure a fixed time interval during which the control relay is adapted to be operated by said electrical relay and thereby advance the first namedrotary switch beyond said predetermined setting, an electro-responsive counting device adapted to be actuated by the first named rotary switch as the rotary switch moves beyond said predetermined setting, a firing circuit, and means settable at will for causing the firing circuit to be closed by the counting device when the counting device has made a predetermined number of successive operations.

6. In a mine adapted to be moored ata predetermined depth of submersion within a body of water, the combination of means for firing the mine in responseto a predetermined number of pairs of signals corresponding respectively-to changes in the magnetic field vector parallel to the major axis of the mine and adjacent the mine when the signals of-each pair are received in predetermined time spaced relation, an induction pickup coil arranged within the mine adapted to generate electrical signals corresponding respectively to changes in said magnetic field vector, means controlled 'by said signals for operating the mine firing means selectively in accordance with the strength of the signals, and means for mooring the mine with the axis of said induction pickup coil arranged in a vertical position regardless of the flow of water past the mine thereby to prevent the generation of an electrical signal by angular movement of the induction pickup coil in response to said flow sufiicient to operate the mine firing means. i 1

7. In a mine adapted to be moored Within a body of 'water at a predetermined depth of submersion, the combination of means includingan electrical relay for sensing variations in the magnetic field adjacent the mine, an electro-respon sive timing device controlled by said relay and adapted to close a control circuit in predetermined time spaced relation with respect to the operation of the relay, said timing device having an initial position and an intermediate position, a rotatable switch mechanism adapted to measure a predetermined interval of time, means controlled by said control circuit for setting said switch mechanism in operation, a counting device having a contact element moveable to a plurality of diflerent positions, a plurality of electrical contacts adapted to be engaged in succession by said contact element, means controlled by said electro-responsive timing device for actuating the contact element of said counting device into engagement withthe next succeeding electrical contact as the electro-responsive timing device is moved beyond said intermediate position, means controlled by the electrical relay in response to a variation in the magnetic field adjacent the mine for moving said electro-responsive timing device beyond said intermediate position during said predetermined interval of time, a detonating device, means settable at will for operatively connecting said detonating device selectively to the contacts of said counting device,

by said sensitive relay adapted to cause the rotary switch to be moved from said home position and from said intermediate position, means adapted to arrest the rotary switch in said intermediate position for a predetermined interval of time, a second rotary switch adapted to measure said predetermined interval of time, means including an additional pair of slow releasing relays for setting said second rotary switch in operation as the first named rotary switch moves into said intermediate position, an electroresponsive counting device having a rotatable contact element adapted to engage a plurality of contacts in succession as the counting device is successively operated,

means for selectively operating said counting device as the first named rotary switch is moved from said intermediate position, a release relay adapted to be operated by said second rotary switch when said predetermined interval of time has been measured, means including circuit closing contacts on said release relay for causing the first named rotary switch to be advanced from said intermediate position to said home position when the first named rotary switch has remained in the intermediate position throughout said predetermined interval of time, and circuit interrupting means on said release relay adapted to prevent the operation of the counting device by said first named rotary switch as' the first named rotary switch moves from said intermediate position.

9. In a submarine minevof the character disclosed arranged within amagnetic field, means including a relay for detecting a plurality of pairs of changing conditions within said field and ge'nerating",sigi1als corresponding respectively to each of said changing conditions, means con trolled by said relay for making and retaining an elec' trical connection corresponding to the first changing condition of each of said pairs detected by said detecting means, means including a rotary switch for measuring a predetermined interval of time after said connection has been made, a pair of slow releasing relays operatively connectedto said rotary switch and adapted to cause the switch to ,be advanced periodically to the next successive setting duringsaid predetermined interval of time, an electro-responsive device adaptedto count the numberof pairs of signals corresponding respectively to changing conditions within the magnetic field detected by said detecting means, means for interrupting said stored connection as the second changing condition within the magnetic field of said pair is detectedby said detecting means during said predetermined interval of time, means for causing said electro-responsive device to count the second signal of each pair as said connection is interrupted, and means including a detonator for causing the mine to explode when a predetermined number of signals have been counted by said electro-responsive device.

10,, In a submarine mine of the character disclosed arranged within a magnetic field, means including a sensitive relay for detecting a changing condition within said magnetic field, a control relayoperatively connected to said sensitive relay and adapted to be operated thereby, an electro-responsive stepping switch having a plurality of switch wipers settable to an initial home position and adapted to engage a plurality of contacts in succession corresponding to different positions of the switch, switch stepping means, means including a pair of slow releasing relays for causing the, switch to he stepped ahead by said switch stepping meansunder controlof saidcontrol relay, means controlled by said switch for forcibly restoring said sensitive relay to, an initial unoperated condition when the switch has stepped ahead to a predetermined position, means controlled by theswitch for preventing the release of said control relay while the switch is in said predetermined position, meanscontrolled by the switch for releasing said control relay as the switch steps to the next succeeding position beyond said predetermined position thereby to arrest the switch in said ,next succeeding position, a second stepping switch having an initial starting position and adapted to measure apredetermined interval of time, means for operating said second stepping switch, means controlled by said switch stepping means for setting said second stepping switch in operation as the first named stepping switch moves into said next succeeding position, means including said pair of slow releasing relays for causing the first namedstepping switch to he stepped ahead in responseto a change in the magnetic field detected by said detecting means during said predetermined interval of time, means controlled by said first named switch for making a plurality of electrical connections in successive order, each of said connections corresponding respectively to changing conditions in the magnetic fielddetected during said predetermined interval of time, means controlled by said second stepping switch for causing thefirst named stepping switch to be stepped ahead at a more rapid rate to said initial home position when the second stepping switch has measured said predetermined interval of time, and means controlled by the first named stepping switch as the switch wipers thereof move into the initial home position for causing said second stepping switch to be stepped ahead to said starting position.

11. In a submarine mine of the character disclosed arrelay for'detecting a-changing condition withinjsaid magnetic field, -a control relay adapted to be operated'by said sensitive:relay,--anelectro-responsive stepping switch having a plurality .ofvswitchwiperssettable to an initial home position and adapted to engage a plurality of contacts in succession corresponding 'to different positions of the switch, switch stepping means, means including a pair of slow releasing relays for causing the switch to be stepped ahead by said switch stepping means under control of said control relay, means controlled by said switch for forcibly restoring said sensitive relay to an initial lunoperated condition when the switch has stepped ahead to a predetermined position, means controlled by the switch for preventing the release of said control relay while the switch is in said predetermined position, means controlled by the switch for releasing said control relay as the switch steps to the next succeeding position beyond said predetermined position thereby to arrest the switch in said next succeeding position, a second stepping switch having an initial starting position and adapted to measure a predetenmined interval of time, means for operating said second stepping switch, means controlled by said switch stepping means for setting said second stepping switch in operation as the first named stepping switch moves into said next succeeding position, means including said pair of slow releasing relays for causing the first named stepping switch to be stepped ahead in response to a change in the magnetic field detected by said detecting means during said predterrnined interval of time, means controlled by said first named switch for setting up in successive order a plurality of electrical connections corresponding respectively to changing conditions in the magnetic field detected during said predetermined interval of time, means controlled by said second stepping switch for causing the first named stepping switch to be stepped ahead at a more rapid rate to an initial home position when the second stepping switch has measured said predetermined interval of time, detonating means, and means for firing said detonating means when a predetermined electrical connection has been set up.

12. In a submarine mine of the character disclosed arranged within a magnetic field, an induction pickup coil having a sensitive relay operatively connected thereto adapted to detect a changing condition within said magnetic field, an electromagnet adapted to reset the sensitive relay forcibly to an initial unoperated position regardless of the changing condition within said magnetic field, a steppng switch device having an initial home position and a plurality of moved positions, means including a control relay adapted to be operated by said sensitive relay for stepping the switch ahead to eachof said moved positions and to said home position respectively,

means controlled by said stepping switch for operating said reset electromagnet when the switch has made a predetermined number of steps and for releasing the reset electromagnet when the switch has made an additional step, a device for measuring a predetermined interval of time, means eifective as the stepping switch moves ahead during said additional step for setting said time measuring device in operation, means for arresting the switch in the moved position corresponding to said additional step, and means responsive to an impulse of pressure received through the water adapted to operate said reset electromagnet during the movement of the stepping switch to said predetermined position and while the switch is in the moved position corresponding to said additional step.

13. In a mine firing mechanism of the character disclosed arranged within a magnetic field, means including an induction pick-up coil and a sensitive relay electrically connected thereto for detecting changes in said magnetic field, means controlled by said relay for counting pairs of changes in said field occurring in predetermined time relation within a predetermined period of time, .a detonating device, and means settable at will to differentsettings respectively corresponding to different numbers-and operatively connected to said counting means for causing the mine to be fired by said detonatingdevice when the number *of pairs of changes in the magnetic field counted'by said counting means is equal to the numberof the instant setting. V V V 1:4,;111- a submarine rnine of the character disclosed arranged within a magnetic field, means including an electrical relay for detecting a plurality of changing conditions within said field, a switching device controlled by said relay and settable from an initial setting to a second setting in response to a first change in said magnetic field detected by said detecting means, normally inactive electromagnetic means operable in unit cycles for measuring a predetermined interval of time, means on said switching device for setting said time measuring means in operation as the switching device is set to said second setting, means for causing the switching device to be actuated from said second setting to said initial setting in response to a second changing condition of said field detected by said detecting means within said predetermined interval of time, electromagnetic means for counting the number of second changing conditions detected during succeeding cycles of operations of said time measuring means, and means controlled by the time measuring means for actuating the switching device from said second setting to the initial setting thereof when said second changing condition within the field is not detected by the detecting means during one of said cycles of operations.

15. The combination of a sequence selecting switch mechanism including a relay adapted to close a set of contacts in response to a signal of predetermined character received thereby, a source of signals operatively connected thereto, a first rotary stepping switch having a normal setting and adapted to be advanced to a predetermined setting upon the first closure of said contacts, a pair of contacts on said switch closeable as the switch moves to an off normal position, means controlled by said pair of contacts for controlling the rate of advance of said rotary switch, a second rotary stepping switch adapted to be advanced step by step from its initial position one complete revolution in response to movement of said first rotary stepping switch to said predetermined setting, a plurality of electromagnetic time delay relays interconnected in additive time delay relation for limiting the rate of stepping of the second rotary stepping switch whereby a predetermined time interval is established for a complete revolution of the second rotary stepping switch, electromagnetic means operatively connected through a contact of said second stepping switch to cause the first rotary stepping switch to return to the normal position thereof as the second rotary stepping switch completes one revolution whereby the mechanism is returned to normal following any initiation of operation thereof lacking the predetermined number and character of signals, and switching connections on the first rotary stepping switch adapted to apply battery to an external circuit when a predetermined number of closures of said relay are obtained during said time interval.

16. In a switch combination for selecting signal sequences, relay means for selecting signals of a predetermined character, a source of signals to be selected in sequential order by said relay means, rotary switch means for registering the number of said signals selected within a sequence, means for limiting the period within which signals of a sequence may be selected, said limiting means including a plurality of electromagnetic time delay relays interconnected to employ additively the delay times thereof and a stepping switch advanceable in steps at intervals corresponding to the sum of said delay times, homing means on the rotary switch and controlled by said period limiting means and effective after said time has expired for returning the rotary switch to an initial position thereof, and circuit connecting means controlled by the rotary switch means and adapted to apply power to an f 23 z 24 external circuit in response to registration of a prede- 1,382,374 Maxim June 21, 1921 termined number of selected signals within said pe 1,390,768 Dorsey Sept. 13, 1921 I 1,466,915 N' h l S t. 4, 1923 References Cited in the file Of this patent 2 54 et 3; 46

UNITED STATES PATENTS 5 953,181 Bergstrom Mar. 29, 1910 FOREIGN PATENTS 1,310,568 Heap et a1. July 22, 1919 5112401 Sweden 1360-5. 1919 

